package 加密与安全;

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;
import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;

import org.apache.commons.codec.binary.Hex;

/**
 * DH安全编码组件  属非对称加解密
 * 
 * @author 
 * @version 1.0
 * @since 1.0
 */
public abstract class DHCoder{
	
	public static final String ALGORITHM = "DH";

	/**
	 * 默认**字节数
	 * 
	 * <pre>
	 * DH
	 * Default Keysize 1024  
	 * Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive).
	 * </pre>
	 */
	private static final int KEY_SIZE = 1024;

	/**
	 * DH加密下需要一种对称加密算法对数据加密，这里我们使用DES，也可以使用其他对称加密算法。
	 */
	public static final String SECRET_ALGORITHM = "AES";
	private static final String PUBLIC_KEY = "DHPublicKey";
	private static final String PRIVATE_KEY = "DHPrivateKey";

	/**
	 * 初始化甲方**
	 * 甲方构建密钥对儿，将公钥公布给乙方，将私钥保留；双方约定数据加密算法；
	 * 
	 * @return
	 * @throws Exception
	 */
	public static Map<String, Object> initKey() throws Exception {
		
		KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
		keyPairGenerator.initialize(KEY_SIZE);

		KeyPair keyPair = keyPairGenerator.generateKeyPair();

		// 甲方公钥
		DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

		// 甲方私钥
		DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

		Map<String, Object> keyMap = new HashMap<String, Object>(2);

		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);
		return keyMap;
	}

	/**
	 * 初始化乙方**
	 * 乙方通过甲方公钥构建密钥对儿，将公钥公布给甲方，将私钥保留。
	 * 
	 * @param key 甲方公钥
	 * @return
	 * @throws Exception
	 */
	public static Map<String, Object> initKey(byte[] key) throws Exception {
		// 解析甲方公钥
		//byte[] keyBytes = decryptBASE64(key);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(key);
		KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
		PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);

		// 由甲方公钥构建乙方密钥对
		DHParameterSpec dhParamSpec = ((DHPublicKey) pubKey).getParams();

		KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(keyFactory.getAlgorithm());
		keyPairGenerator.initialize(dhParamSpec);

		KeyPair keyPair = keyPairGenerator.generateKeyPair();

		// 乙方公钥
		DHPublicKey publicKey = (DHPublicKey) keyPair.getPublic();

		// 乙方私钥
		DHPrivateKey privateKey = (DHPrivateKey) keyPair.getPrivate();

		Map<String, Object> keyMap = new HashMap<String, Object>(2);

		keyMap.put(PUBLIC_KEY, publicKey);
		keyMap.put(PRIVATE_KEY, privateKey);

		return keyMap;
	}

	/**
	 * 加密
	 * 甲方使用私钥、乙方公钥、约定数据加密算法构建本地密钥，然后通过本地密钥加密数据，
	 * 
	 * @param data  待加密数据
	 * @param publicKey  甲方公钥
	 * @param privateKey  乙方私钥
	 * @return
	 * @throws Exception
	 */
	public static byte[] encrypt(byte[] data, byte[] publicKey,byte[] privateKey) throws Exception {

		// 生成本地**
		SecretKey secretKey = getSecretKey(publicKey, privateKey);
		System.out.println("生成本地**");
		// 数据加密
		Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
		cipher.init(Cipher.ENCRYPT_MODE, secretKey);

		return cipher.doFinal(data);
	}

	/**
	 * 解密
	 * 
	 * @param data  待解密数据
	 * @param publicKey 乙方公钥
	 * @param privateKey 乙方私钥
	 * @return
	 * @throws Exception
	 */
	public static byte[] decrypt(byte[] data, byte[] publicKey,byte[] privateKey) throws Exception {

		// 生成本地**
		SecretKey secretKey = getSecretKey(publicKey, privateKey);
		
		// 数据解密
		Cipher cipher = Cipher.getInstance(secretKey.getAlgorithm());
		cipher.init(Cipher.DECRYPT_MODE, secretKey);

		return cipher.doFinal(data);
	}

	/**
	 * 构建密钥对
	 * 
	 * @param publicKey 公钥
	 * @param privateKey 私钥
	 * @return
	 * @throws Exception
	 */
	private static SecretKey getSecretKey(byte[] publicKey, byte[] privateKey) throws Exception {
		// 初始化公钥
		//byte[] pubKeyBytes = decryptBASE64(publicKey);

		KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKey);
		PublicKey pubKey = keyFactory.generatePublic(x509KeySpec);
		// 初始化私钥
		//byte[] priKeyBytes = decryptBASE64(privateKey);

		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(privateKey);
		Key priKey = keyFactory.generatePrivate(pkcs8KeySpec);

		KeyAgreement keyAgree = KeyAgreement.getInstance(keyFactory.getAlgorithm());
		keyAgree.init(priKey);
		keyAgree.doPhase(pubKey, true);

		// 生成本地**
		SecretKey secretKey = keyAgree.generateSecret(SECRET_ALGORITHM);
      System.out.println("加密密钥:"+Hex.encodeHexString(secretKey.getEncoded()));
		return secretKey;
	}

	/**
	 * 取得私钥
	 * 
	 * @param keyMap
	 * @return
	 * @throws Exception
	 */
	public static byte[] getPrivateKey(Map<String, Object> keyMap) throws Exception {
		Key key = (Key) keyMap.get(PRIVATE_KEY);

		return key.getEncoded();
	}

	/**
	 * 取得公钥
	 * 
	 * @param keyMap
	 * @return
	 * @throws Exception
	 */
	public static byte[] getPublicKey(Map<String, Object> keyMap) throws Exception {
		Key key = (Key) keyMap.get(PUBLIC_KEY);

		return key.getEncoded();
	}

}


